A door latch device is provided inside a door of a vehicle such as a motor vehicle to hold the door in a closed position. The door latch device can be shifted between a locking state and an unlocking state by driving an actuator unit and operating a manual control means such as a lock knob or the like.
In relation to the above-described actuator unit, the applicant discloses a configuration including a worm wheel which is rotated by a worm secured to a drive shaft of a motor and a lock lever capable of rotating on a shaft center thereof is parallel to a shaft center of the worm wheel in PTLs 1, 2, for example. In this configuration, the worm wheel is rotated by driving the motor, and the lock lever is pressed by projecting portions formed on rotational surfaces of the worm wheel to be shifted between a locking position and an unlocking position, whereby the door latch device connected to the lock lever can be shifted between the locking state and the unlocking state. For example, when the lock lever is shifted from the locking position to the unlocking position, the lock lever is pressed to the unlocking position by the projecting portion formed on one rotational surface of the worm wheel which is driven to rotate by the motor, while the projecting portion formed on the other rotational surface is brought into abutment with the lock lever, whereupon the shifting operation is completed.
Incidentally, in the door latch device, it is necessary to permit a manual operation by a manual control means whether the lock lever is located either in the locking position or in the unlocking position. This requires the actuator unit to be able to rotate only the lock lever between the locking position and the unlocking position wherever the worm wheel stops.
Then, in the case of the actuator unit according to the related art, the projecting portion on each of the rotational surfaces of the worm wheel is configured, for example, so that two tooth portions extend in a 180-degree direction from a rotational center of the worm wheel. Then, a space between both the tooth portions is secured wide, and the projecting portions on both the rotational surfaces have a symmetrical shape. Thus, the manual operation is permitted in an ensured fashion by this configuration.